System for rapidly positioning gimbaled objects

ABSTRACT

A system for rapidly positioning gimbaled objects utilizing a rotating mass stabilization technique in conjunction with a brake and motor at each gimbal trunnion. With the alternate activation and energizing of a preselected motor and brake, the gimbaled object can be rapidly positioned with a minimum of torque.

United States Patent Eckhardt Mar. 5; 1974 [5 SYSTEM FOR RAPIDLYPOSITIONING 2,893,248 7/1959 Ecary 102 010. 3 G A OBJECTS 2,592,4174/1952 Hale lO2/DlG. 3

[75] Inventor: Homer D. Eckhardt, Lincoln, Mass.

[73] Assignee: The United States of America as Primary ExaminerManuel A.Antonakas represened by the Air Force, Washington, DC.

[22] Filed: Dec. 13, 1972 211 Appl. No.: 314,622 [571 ABSTRACT 52 Us.(:1. 74/s.4 244/1 SA A System for rapidly psitining gimba'ed 51 Int. Cl..01c 19/00 Zing a Mating mass stabilizatim echnique in 5 Field ofSearch" 74/54 5A5 5 47 5 42 522 junction with a brake and motor at eachgimbal truni 244/1 sAfloz/bls. nion. With the alternate activation andenergizing of a preselected motor and brake, the gimbaled object can[56] Reierences Cited be rapidly positioned with a minimum of torque.

UNITED STATES PATENTS 2,801,544 8/1957 Wagner 102 1310. 3 7 Claims, 1Drawing Figure PAIENIEDRAR 3,795,150

BACKGROUND OF THE INVENTION This invention relates generally to a systemfor applying positioning torque to a gimbaled object and, moreparticularly, to a system which requires only modest torque for rapidlypositioning a gimbaled object such as a stabilized platform.

There exists in numerous fields a need for accurately stabilizedplatforms. Such a stable platform is used to maintain angular referencedirections in inertial space. The most effective application of a stableplatform is made by inertial navigation systems which depend upon theplatform for fixity to an extreme degree. In principle, a platform driftof one degree of arc can lead to a navigating error of 60 nauticalmiles. Furthermore, these platformsnot only find use in navigationalsystems, but they also find application in any area wherein an object orinstrument such as telescopes or radar must be stabilized.

The platform itself and any object mounted thereon usually has at leasttwo degrees of freedom. This platform is preferably rotatably supportedby a frame through the use of a first set of trunnions or supportingshafts with the frame in turn supported by a second set of trunnionswhich are orthogonal to the first set. In such a system, additionalmeans are provided for rapidly positioning the platform and formaintaining its stable position. Generally, such a stabilized platformis mechanized by using two or more gyroscopes to sense rotation of theplatform from the desired orientation and driving means to torque theplatform in order to resist this rotation. Such an arrangement, however,is

complex in nature, extremely expensive'in construction and stillrequires large amounts of torque produced by large torquing motors if itis so desired to rapidly position the platform and any objects thereon.

In order to alleviate some of the problems set forth hereinabove it ispossible to stabilize a platform by mounting a rapidly spinning mass inbearings which are rigidly attached to the platform. Such a spinningmass will tend to spatially stabilize any line on the platform which isparallel to the axis about which the mass is spinning. This systemeliminates the use of stabilizing gyroscopes and is thereforepotentially simpler and cheaper than the use of gyroscopes acting inservoloops and therefore desirable in platform systems which do notrequire three degree of freedom stabilization. The spinning mass system,however, requires large angular momentum of the spinning mass for goodstabilization of the platform. Therefore, extremely large torques mustbe applied about the gimbal axis to produce any rapid angular motion ofthe platform about any axes other than one parallel to the axis of spinof the spinning mass. Although small angular changes can be per formedrelatively easily with the spinning mass technique, the large torquerequirement has prevented the application of a spinning massstabilization technique from becoming acceptable in systems where rapidrepositioning is needed. Any further modifications of this system merelyincrease the complexity of construction and operation and thereforeproduce many of the problems encountered with other prior artstabilization and repositioning techniques. It is therefore clearlyevident that a major problem arises in the field of spin stabilizedgimbaled objects when it becomes necessary to rapidly position such anobject for whatever reason.

SUMMARY OF THE INVENTION The instant invention sets forth a system whichis capable of rapidly positioning gimbaled objects utilizing thespinning mass technique with a minimum of torquing power. In thisinvention each of the gimbal trunnions of a spinning mass stabilizedplatform is provided with a brake or any other suitable actuatablefriction, locking or restraining device in conjunction with a torquemotor. This combination allows for the use of an extremely small torquemotor, contrary to the large torquing requirements of the past. In orderto rotate the platform rapidly to a new orientation with the instantinvention, the brake or friction device is applied to one gimbal axiswhile the torque motor on the other axis is activated to produce aplatform rotation about this second axis until the desired rotation ofthe platform has been achieved. When the desired rotation about thissecond gimbal axis has been attained the brake on the first gimbal axisis released, the torque motor on the second axis is deactivated, and theplatform rotation stops. The process is then repeated with the brake onthe second axis activated and the torque motor on the first axisactivated to produce the desired rotation about the first axis.

The motor torque required with the system of this invention is verymodest even for large rotation rates of the spinning mass because thebrake or friction device has reduced the stabilized platform to thestatus of a single degree of freedom gyroscope. Thus, the desiredplatform orientation has been achieved very rapidly and any subsequentminor positioning control can be accomplished by merely activating themotors without energizing the braking means.

It is therefore an object of this invention to provide a system forrapidly positioning spin stabilized gimbaled objects with theutilization of small torquing power.

It is another object of this invention to provide a system for rapidlypositioning gimbaled objects which is economical to produce and whichutilizes conventional, currently available components that lendthemselves to standard mass producing techniques.

For a better understanding of the present invention together with otherand further objects thereof reference is made to the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims.

DESCRIPTION OF THE DRAWING The only FIGURE of this drawing is apictorial view of the system of this invention for rapidly positioninggimbaled objects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now madeto the only FIGURE of the drawing which shows in pictorial fashion thesystem 10 of this invention which is utilized to rapidly position anygimbaled object such as a stable platform 12. This platform 12 may takeon any desired configuration, it may be in the form of a telescope,radar or the like or it may contain any suitable instruments eitherwithin or thereupon. Platform 1.2 is a spin stabilized platform and ismounted on gimbals such as frame M and shaft 16.

This arrangement allows platform 12 to have two degrees of rotationalfreedom relative to mounting base 18. A rotating mass of any suitableconfiguration is rotatably secured along the axis 21 of platform 12 andits rapid spinning produced by any suitable motor 23 about axis 21 tendsto hold platform 12 such that axis 21 remains at a steady inertialorientation.

Any suitable torquing motors 22 and 24 are mounted upon base 18 andframe 14 respectively. Motor 22 is operably connected in anyconventional manner to shaft 26 of frame 14 while motor 24 is operablyconnected in any conventional manner to shaft 16, the operation of whichwill be described hereinbelow.

Under ordinary circumstances with platform 12 sta bilized by therotation of mass 20, activation of motor 22 tending to rotate shaft 26in the direction of arrow A causes the rotation of platform 12 about theY axis in the direction of arrow A. Likewise, an activation of motor 24tending to rotate shaft 16 in the direction of arrow B causes rotationof platform 12 in the direction of arrow B about the X axis. This typeof arrangement performs adequately for any slow minor positional changeof platform 12. However, because of the large angular momentum requiredof spinning mass 20 necessary for good stabilization of platform 12,extremely large torques must be applied about the gimbal axes X and Y toproduce rapid angular motion of the stabilized platform 12. This largetorque requirement is virtually prohibitive when a gimbaled object is tobe rapidly repositioned.

The instant invention utilizes a brake or other actuable friction orrestraining devices 28 and 30 in conjunction with motors 22 and 24,respectively. With the system set forth in this invention, rapidrotation of platform 12 to any desired orientation can be easilyaccomplished with minimum power from motors 24 and 22, respectively,when brakes or friction devices 28 and 30 are alternately energized andde-energized in a manner to be set forth hereinbelow.

For example, when one wishes to rapidly change the angular position ofplatform 12 about the Y axis it is merely necessary to energize brakingmeans 28 locking frame 14 in place and apply only a modest torque frommotor 24 so as to rotate platform 12 about the Y axis. If it is furtherdesired to rotate platform 12 about the X axis one must merely apply thebrake 30 to lock shaft 16 and platform 12 and apply a modest torque frommotor 22 so as to accomplish rotation about the X axis. ln bothinstances platform 12 will rotate in the same direction as the torqueapplied by either motor 22 or 24. When the desired gimbal angle has beenobtained it is merely necessary to de-energize the appropriate brake 28or 30 the appropriate torque motor 24 or 22 and the rotation of platform12 will stop and stabilize. Any further minor slow repositioning can beaccomplished without the energizing of brakes 28 and 30 by torque motors22 and 24 by the conventional manner set forth hereinabove.

It is therefore clearly evident that system 10 of this invention whichincorporates therein a plurality of brakes 28 and 30 as well as thespinning mass stabilization technique is inexpensive in construction,simple in operation.

Although this invention has been described with reference to aparticular embodiment it will be understood to those skilled in the artthat this invention is also capable of a variety of alternateembodiments within the spirit and scope of the appended claims.

I claim:

ll. In a system for rapidly positioning gimbaled objects having amounting base, first means rotatably mounted on said base for supportingsaid object for rotation about a first axis, second means rotatablymounted on said first means for supporting said object for rotationabout a second axis, first driving means for rotating said firstsupporting means about said first axis and second driving means forrotating said second supporting means about said second axis wherein theimprovement therein comprises a mass rotatably mounted along an axis ofsaid gimbaled object, means for spinning said mass, a first retardingmeans operably connected to said first driving means for preventingrotation of said first supporting means with respect to said base, andsecond retarding means for preventing rotation of said second supportingmeans with respect to said first supporting means, whereby energizing ofsaid first retarding means and simultaneous activation of said seconddriving means causes rapid positioning of said gimbaled object aboutsaid second axis while energizing of said second retarding means andsimultaneous activation of said first driving means causes rapidpositioning of said gimbaled object about said first axis.

2. In a system for rapidly positioning gimbaled ob jects as defined inclaim 1 wherein said first and second retarding means are in the form ofbrakes.

3. In a system for rapidly positioning gimbaled objects as defined inclaim 2 wherein said gimbaled object is a stabilized platform.

4. ln asystem for rapidly positioning gimbaled objects as defined inclaim 3 wherein said first supporting means is a frame having a shaftfor rotatably securing said frame to said base.

5. In a system for rapidly positioning gimbaled objects as defined inclaim 4 wherein said second supporting means is a shaft rotatablysecured within said frame and said platform is mounted on said shaft forrotation therewith.

6. A method of rapidly positioning a gimbaled object comprising thesteps of stabilizing said object by rotating a mass secured thereto,preventing rotation of said gimbaled object'about a first axis andapplying a relatively small torque to said gimbaled object about asecond axis thereby causing said gimbaled object to rapidly rotate aboutsaid second axis.

7. A method of rapidly positioning a gimbaled object as defined in claim6 further comprising the steps of preventing rotation of said gimbaledobject about said second axis and applying a relatively small torque tosaid gimbaled object about said first axis thereby causing said gimbaledobject to rapidly rotate about said first axis.

1. In a system for rapidly positioning gimbaled objects having amounting base, first means rotatably mounted on said base for supportingsaid object for rotation about a first axis, second means rotatablymounted on said first means for supporting said object for rotationabout a second axis, first driving means for rotating said firstsupporting means about said first axis and second driving means forrotating said second supporting means about said second axis wherein theimprovement therein comprises a mass rotatably mounted along an axis ofsaid gimbaled object, means for spinning said mass, a first retardingmeans operably connected to said first driving means for preventingrotation of said first supporting means with respect to said base, andsecond retarding means for preventing rotation of said second supportingmeans with respect to said first supporting means, whereby energizing ofsaid first retarding means and simultaneous activation of said seconddriving means causes rapid positioning of said gimbaled object aboutsaid second axis whIle energizing of said second retarding means andsimultaneous activation of said first driving means causes rapidpositioning of said gimbaled object about said first axis.
 2. In asystem for rapidly positioning gimbaled objects as defined in claim 1wherein said first and second retarding means are in the form of brakes.3. In a system for rapidly positioning gimbaled objects as defined inclaim 2 wherein said gimbaled object is a stabilized platform.
 4. Inasystem for rapidly positioning gimbaled objects as defined in claim 3wherein said first supporting means is a frame having a shaft forrotatably securing said frame to said base.
 5. In a system for rapidlypositioning gimbaled objects as defined in claim 4 wherein said secondsupporting means is a shaft rotatably secured within said frame and saidplatform is mounted on said shaft for rotation therewith.
 6. A method ofrapidly positioning a gimbaled object comprising the steps ofstabilizing said object by rotating a mass secured thereto, preventingrotation of said gimbaled object about a first axis and applying arelatively small torque to said gimbaled object about a second axisthereby causing said gimbaled object to rapidly rotate about said secondaxis.
 7. A method of rapidly positioning a gimbaled object as defined inclaim 6 further comprising the steps of preventing rotation of saidgimbaled object about said second axis and applying a relatively smalltorque to said gimbaled object about said first axis thereby causingsaid gimbaled object to rapidly rotate about said first axis.